The invention describes a method for more efficient way of obtaining mechanical work and/or power generation from fluid flows with the oscillating motion of the blade and the counterweight in a direction that is perpendicular to the flow of fluid in conjunction with a smooth and periodic change of the angle of the blade to the flow of fluid over the sine wave which is characterized by being carried out by: rotating the surface of the blade to the direction of the fluid's flow and/or; changing the amplitude of the oscillation of the blade with respect to the fluid's flow rate and/or; changing the amplitude of the angle of the blade with respect to the fluid's flow rate; capturing mechanical work in the form of torque or tensile/compressive force to propel attached machinery or generate power from the arm of the counterweight. The invention further describes the apparatus to carry out this method.